Date   
Re: Nextion 5" display noise #noise #ubitx #nextion

Justin Phillips K5AXL
 

So, what has two thumbs and is a huge doomarse? <- this guy.

I was on LSB but adjusting the USB setting. 95% of the display noise is gone now.

Re: Are these output watt rating crazy?

 

Hi,

I used the AADE filter simulation/design program.  I posted because I had seem some comments on the power outputs and was curious to simulate the low filter to see if that might impact some of the power levels.  I simulated the lowest filter I saw on the ubitx v3 schematic.  Did I miss a lower one?  This one seems to be the lowest and used for both 40m and 80m with a cutoff very close to 7MHz (actually showed -2dB at 7.3MHz).

Yes the design environment is 50 ohms.  That does not mean the filter will show that for all frequencies.  At the design frequency, they should show that (as this one does for 40m).  At other frequencies they can present higher or lower impedances which will affect power output.  This one does also show around 50 ohms at 80m.  However at 60m it shows to be about 20 ohms and at 160m about 10 ohms.  Even using another filter on the output, with this filter inline it may cause trouble.  So it would be best to have a designed 160m filter linked directly to the output of the PA if one wants to use that band.  My thoughts anyway.

Of course it would be good to see an actual measurement of the filter with a VNA etc.  My equipment is packed away from a move at the moment so I have to rely on software at the moment.

I just thought people may be interested in what I had found.   I can work on my own no problem.




Cheero,


Mark.

Nextion 5" display noise #noise #ubitx #nextion

Justin Phillips K5AXL
 

I have a v5 uBITX in Sunil's 5" case with audio amp kit. Audio sounds just fine until I power the Nextion display. It's got a terrible buzz, and you can hear digital noises when the display changes, or when you turn the encoder. 

I've run separate power for the display and the noise remains. I Also tried powering the display with a battery pack, the noise is just as bad. How do you get this noise out? 

Also, my audio (when not influenced by the display) sounds very tinny and a bit high pitch, and it doesn't seem to change when adjusting the BFO much at all.. any ideas?

Re: Are these output watt rating crazy?

Jerry Gaffke
 

Mark,

I assume you posted to this old thread because
you wanted to tell us about your simulation results.

Yes, the uBitx should not be used on 160m without a suitable LPF
inline with the antenna.  Without that LPF the third harmonic will be
nearly as strong as the fundamental.

Not sure exactly how you went about simulating the filter
or exactly what corner frequency you saw.
Regardless of what your filter program thinks, the 80m LPF
is being used in a more or less 50 ohm environment.
Changing the impedances will change the frequency response.

Attenuating some harmonic by 13dB may or may not be sufficient.
If that particular harmonic coming out of the final amp is already 30dB down
from the fundamental, then the extra 13dB of attenuation from the filter
will be sufficient to meet FCC regs.  Due to the push-pull configuration
of the IRF510 final, it is mostly the 3rd harmonic that gives us grief.

Would be interesting to measure (not simulate) the response of the 80m LPF
using something like the Antuino, driving the filter from a 50 ohm source
and terminating it into 50 ohms.

I believe the 3dB corner frequency of the 80m LPF is around 5mhz,
so if you tried to use it on 40m you would not be putting out much of a signal.
 
Here's the post you quoted    https://groups.io/g/BITX20/message/68292
It happens to be in the same thread as our current conversation,
though this thread hasn't been active for over 6 months.,

Jerry, KE7ER


On Sun, Nov 10, 2019 at 05:30 PM, Mark - N7EKU wrote:
Jerry Gaffke
Apr 25  
The 80m LPF is also used for 60m, so the cut-toff freq is high enough to pass the third harmonic of 160m.This is not a sine wave:    https://groups.io/g/BITX20/message/48122
Hi,

I just entered the lowest ubitx LFP into a filter program and see that it is actually a 40m LPF.  It has a pretty good cutoff, so it cuts off what it need to for 60m and 80m, but would do almost nothing for 160m as it won't cutoff anything until the 4th harmonic and will only do about a 13dB cut there so not really effective until the 5th harmonic.  So basically useless on 160m.

Besides that, the input impedance to the filter on 160m comes out to about 10 ohms so not what the PA is designed to see.  On 60m it shows as 20 ohms a little better, but not great.

73,


Mark.

Re: Wiring question - Nextion case

Mike WA0YCN
 

Thanks guys. 


I ran into the front panel board problem - after I’d soldered the board (I built it first since it was “simplest”j.  The front of the jacks are set back from the edge of the board.  Thankfully, I have a Dremmel and the trace was far enough from the edge that I could ground the board back so things would fit. 

Looking at the pictures for powering the audio amp, agc board and fan (and expecting to add a CW filter later), I’m not crazy about having all those wires soldered to the small contacts below the relay on the bottom of the ubitx board.  I’m thinking about pulling gnd, 12v xmit and 12v rcv to a terminal strip so I can add only one wire each below the board and connect the 3-4 others on the strip. 

Re: Are these output watt rating crazy?

 

Jerry Gaffke
Apr 25  
The 80m LPF is also used for 60m, so the cut-toff freq is high enough to pass the third harmonic of 160m.This is not a sine wave:    https://groups.io/g/BITX20/message/48122
Hi,

I just entered the lowest ubitx LFP into a filter program and see that it is actually a 40m LPF.  It has a pretty good cutoff, so it cuts off what it need to for 60m and 80m, but would do almost nothing for 160m as it won't cutoff anything until the 4th harmonic and will only do about a 13dB cut there so not really effective until the 5th harmonic.  So basically useless on 160m.

Besides that, the input impedance to the filter on 160m comes out to about 10 ohms so not what the PA is designed to see.  On 60m it shows as 20 ohms a little better, but not great.

73,


Mark.

 

Re: Wiring question - Nextion case

Robert Freeman
 

If you want audio into both sides of the headphones, a jumper needs to be soldered from one side to the other.  

73s de NQ0T, Robert

Re: Using Vacuum Tube heathkit as Linear Amplifier for QRP

Robert D. Bowers
 

I've played around with a Kenwood TS520... using a softrock connected in through the filter board.  The combination was in a word AWESOME... if a different radio even thought on frequency, I probably would have heard it (voice QRM became the limiting factor - static and hiss less of a barrier).  I plan on eventually using the softrock as an IF and the filters (and so on) for transmission.  The good thing is that the tuned circuits in the old radio are going to greatly improve the signal, one way or another.  In fact, they should be at least as clean as the best modern unit.

There are more powerful old tube rigs 'out there' - I can think of a KW rig right now that would be awesome as an amp (plus great filtering) for a BitX (or softrock).

Right now I'm trying to get something on the air with 2m SSB/FT8.  Then other projects will follow...

Bob

On 11/9/19 5:01 PM, Gordon Gibby wrote:


Finally got a chance to try my idea of using a heathkit ssb rig as a power amplifier for a QRP rig.   I've seen "amplifiers" for these rigs going for many hundreds of $$$.  I happen to be swimming in ancient heathkits with 2x6146 linear finals and tuned plate circuits on the driver as well (all good for getting rid of unwanted harmonics.....)

Allison gave some much needed advice on this crazy idea months back, and I finally got the chance to try it:

1 watt output from an exciter [I used an icom 718 that was readily availalbe] -- my only "power measurements" are ancient SWR meters with built in diode detectors so these measurements may be fairly INaccurate.

coax over to a 49:1 homebrew balun our group made for matching resonant half-wave antennas:   ours is a simple autotuner with 14 turns total of #18 teflon wire around a FT-240-43 (or FT-140-43) tapped at turn 2 to give us 7:1 turns ratio, 49:1 impedance ratio, and that checked out roughly with an antenna analyzer and some resistors

I loaded the output with 2500 ohms (temporarily made out of 4 10K resistors in parallel because that is all i had)
output of that via 6 inches of small coax to a 0.01 1kv ceramic capacitor connecting to the PLATE circuit of the removed 6CL6 driver, and to a nearby ground.

Output tested only with very brief bursts of CW -- on 80 meters and 20 meters, got approx 40-50 watts output measured also with an ancient swr meter/wattmeter into a 50 ohm load, everything on the Heathkit peaked for output.   Plate current rose appropriately.   Tuning circuit all appeared appropriately.

No obvious signs of any instability in this pilot test.    
Did not make any measurements with spectrum analyzer.   (In due time......)

That heathkit has other problems elsewhere but the finals appeared in fine shape.   Earlier VERY CRUDE measuresments with a siglent oscilloscope and some math suggested that the drive required at the INPUT to the 6CL6 stage would be less than 100 milliwatts, and that the drive required at the output of 6CL6 would be in the single digit watts range.    The above test appears to confirm those crude measurements.   Since it appeared the two 6146's could be driven adequately with single digit watts I opted to temporarily just remove the 6CL6 driver and connect to its (DC powered!!!!!!!  High voltage!)  plate circucit with a 1kv .01 blocking capacitor.   

Quite pleased with this very very initial test.   
At some point I'll repeat with a uBitx, but that's all for right now.
Gordon Gibby

Attachments:


Re: Wiring question - Nextion case

Ian Reeve
 

The pcb does need a little talc to make everything fit.The connectors I suggest are not soldered in until the jacks are fitted and a assembly dry run done.on mine the edge of the pcb needed to be filed back to ensure jacks sufficiently poke through to be fixed with the round threaded fixings.Once that is done assemble the connectors and make sure there is sufficient room for the main pcb.Again on mine the holes for some connector pins was not in perfect alignment.Hope this helps


From: BITX20@groups.io <BITX20@groups.io> on behalf of Justin Phillips K5AXL <dolmdemon@...>
Sent: Sunday, November 10, 2019 9:41:13 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Wiring question - Nextion case
 
On an aside, if you haven't assembled the front panel board yet make sure you solder the digital and analog sockets pulled back towards the edge as much as you can. And when you solder the jacks on, make sure they're pulled forward as much as you can, however much play in the holes you have. Mine is so tight i have to press the harnesses in and a bit of an angle to squeeze them in behind the jacks. The jacks are so far back i couldnt get the nuts to get any thread, I wound up using the old ones from the stock ubitx kit, they seemed to get more thread to bite.

Re: Wiring question - Nextion case

Justin Phillips K5AXL
 

On an aside, if you haven't assembled the front panel board yet make sure you solder the digital and analog sockets pulled back towards the edge as much as you can. And when you solder the jacks on, make sure they're pulled forward as much as you can, however much play in the holes you have. Mine is so tight i have to press the harnesses in and a bit of an angle to squeeze them in behind the jacks. The jacks are so far back i couldnt get the nuts to get any thread, I wound up using the old ones from the stock ubitx kit, they seemed to get more thread to bite.

Re: Wiring question - Nextion case

Justin Phillips K5AXL
 

Yes, which is normally connected to pins 5/2 of the phones jack when no plug is inserted, completing the connection to pin 7 on analog J1 connection. Inserting a plug disconnects J4 (if im observing it correctly). Mine is wired this way and I have audio to the amp with no plug in the jack and no audio to the amp/speaker with phones plugged in.

Re: uBITX Wireup Diagrams on the HF SIGNALS WEBSITE ARE WRONG!! #ubitx #ubitx-help

KG5MG
 

Scott, did you ever get a response from Al, N1AW regarding the CW jack adapter for the uBitx you posted to the group 12/3102018?  I am just starting on my kit and want to use paddles.

Thanks
73
Hamp KG5MG

Re: Wiring question - Nextion case

Mike WA0YCN
 

Looking at the schematic for the front panel board, I’m confused.  Pin 1 of J4 goes to pin 4 of J8 - is that also NC to pin 5 - so its using the speaker output from the ubitx board?

Re: Reducing power

Gordon Gibby
 

I would suggest to just get a non-inductive potentiometer,  put it on the panel, and run tiny coax to it so you have a panel mounted drive controller.  


On Nov 10, 2019, at 14:42, Sascha Bohnet | DL5SMB via Groups.Io <saschabohnet@...> wrote:

There is also another approach by John, VK2ETA, who tried to control SSB and CW power output via software/firmware by changing the clock frequency of the raduino (40 Mhz IF).
I do not understand it fully, but details can be found here.

Re: Using Vacuum Tube heathkit as Linear Amplifier for QRP

Gordon Gibby
 

Thanks very much! I think we’ve got a pretty cool project developing here. 


On Nov 10, 2019, at 13:36, ajparent1/KB1GMX <kb1gmx@...> wrote:

Gordon,

Yes don't.  Those vacuum fats have plat to grid capcitance and if not neutralized
(or even if it is) it will take off and get unhappy.

If anything lower might be the thing.  The key is you need enough RF grid voltage
to drive the tube but likley less than the total bias needed to get plate current.
Some tubes gt really unhappy or terribly non linear if they see grid current flow.

Grounded grid has some of the same issues but offers a naturally lower input
impedance and a bit less gain.

Allison

Re: Reducing power

Sascha Bohnet | DL5SMB
 

There is also another approach by John, VK2ETA, who tried to control SSB and CW power output via software/firmware by changing the clock frequency of the raduino (40 Mhz IF).
I do not understand it fully, but details can be found here.

Re: Reducing power

ajparent1/kb1gmx
 

Please observe the schematic of the radio board.

Resistor RV1  is there to serve that function.  

NOTE; if you turn it down (clockwise, yes its odd) for 5W on 80M
you will get less power on successive bands.  

Allison

Re: Wiring question - Nextion case

Justin Phillips K5AXL
 

It's coming from J4 on the front panel mic/key/phones board.

Reducing power

R. Tyson
 

Hi,
I have a uBitX to build over the Christmas period. I will be using the KD8CEC firmware and Nextion 2.8" screen
Is there an easy way of altering the output power, short of dropping the supply voltage ? If I could make this easily adjustable....

I like to run QRP CW so that means no more than 5 watts output.
Any ideas appreciated to save me re-inventing the wheel.

Thanks,

Reg

Wiring question - Nextion case

Mike WA0YCN
 

Folks,

I have the AmatuerRadioKits 3.5 Nextion case kit and a recent v5 ubitx.  I’m trying to determine where to get the audio input for the audio amp board that comes with the kit.  The picture in the downloads shows a connection on an earlier version of the ubitx.

Thanks.

Mike
WA0YCN